Class Note

Class Note
Date: 07/05/2021
Akij Mia
ID: 1925102504
Course Title: Data Communication
Course Code: Cse-313

1. What is data communication?
Ans: Data communication are the exchange of data between two devices by some
form of transmission medium of such as a wire cable.
Diagram:-
➢ Message: It is the information or data to be communicated. It can consist of text
numbers, pictures, sound or video or any combination of these.
➢ Sender: It is the device/computer that generates and sends that message.
➢ Receiver: It is the device or computer that receives the message. The location of
receiver computer is generally different from the sender computer. The distance
between sender and receiver depends upon the types of network used in
between.
➢ Medium: It is the channel or physical path through which the message is carrier
from sender to the receiver. The medium can be wired like twisted pair wire,
coaxial cable, fiber-optic cable or wireless like laser, radio waves, and
microwaves.
➢ Protocol: It is a set of rules that govern the communication between the
devices. Both sender and receiver follow same protocols to communicate with
each other.
https://ecomputernotes.com/computernetworkingnotes/communication-networks/what-is-datacommunication
(reference)

2. What is Node?
Ans: A node is a device or data point in a larger network. A node can be a couple of
different things depending on whether the conversation is about computer science or
networking.
In networking a node is either a connection point, a redistribution point, or a
communication endpoint. In computer science, nodes are devices or data points on a
large network, devices such a PC, phone, or printer are considers nodes.
In general, a node has a programmed or engineered capability that enables it to
recognize, process, or forward transmissions to other nodes.
3. How many types of Computer Network?
1. PAN (Personal Area Network)
2. LAN (Local Area Network)
3. MAN (Metropolitan Area Network)
4. WAN (World Area Network)
➢ PAN: PAN is a computer network formed around a person. it can be used for
establishing communication among these personal devices for connecting to a
digital network and the internet.
❖ Characteristics
✓ PAN includes mobile devices, tablet, and laptop.
✓ It can be wirelessly connected to the internet called WPAN.
❖ Advantages of PAN
✓ PAN networks are relatively secure and safe
✓ It offers only short-range solution up to ten meters
✓ Strictly restricted to a small area
❖ Disadvantages of PAN
✓ It may establish a bad connection to other networks at the same
radio bands.
✓ Distance limits.

➢ LAN: A local area network is a group of computer and peripheral devices which
are connected in a limited area such as school, laboratory, home, and office
building.
❖ Characteristics:
✓ LAN is a private network, so an outside regulatory body never
controls it.
✓ LAN operates at a relatively higher speed compared to other WAN
systems.
❖ Advantages:
✓ Data of all network users can be stored on a single hard disk of the
server computer.
✓ LAN operates at a relatively higher speed compared to other WAN
systems.
✓ You can easily transfer data and messages over networked
computers.
✓ Local Area Network offers the facility to share a single internet
connection among all the LAN users.
❖ Disadvantage:
✓ LANs are restricted in size they cover a small area like a single
office, single building or a group of nearby buildings.
✓ The initial setup costs of installing Local Area Networks is high
because there is special software required to make a server.
➢ MAN: A Metropolitan Area Network is consisting of a computer network across
an entire city, college campus, or a small region. It allows you to cover an area
from several miles to tens of miles.
❖ Characteristics:
✓ It mostly covers towns and cities in a maximum 50 km rang.
✓ Mostly used medium is optical fibers, cables
❖ Advantages:
✓ It offers fast communication using high-speed carriers, like fiber
optic cables.
✓ The dual bus in MAN network provides support to transmit data in
both directions concurrently.
✓ A MAN network mostly includes some areas of a city or an entire
city.

❖ Disadvantages:
✓ You need more cable to establish MAN connection from one place
to another.
✓ In MAN network it is tough to make the system secure from hackers
➢ WAN: Wide Area Network is another important computer network that which is
spread across a large geographical area. It is mostly limited to an enterprise or
an organization.
❖ Characteristics
✓ It connect devices that are separated by a broader geographical
area than a LAN
✓ It use serial connection.
❖ Advantages
✓ WAN helps you to cover a larger geographical area. Therefore
business offices situated at longer distances can easily
communicate.
✓ It use serial connection.
❖ Disadvantage:
✓ The initial setup cost of investment is very high.
✓ It is difficult to maintain the WAN network. You need skilled
technicians and network administrators.
✓ Offers lower security compared to other types of networks.
https://www.guru99.com/types-of-computer-network.html (reference)

4. What is NIC?
Ans: A network interface card is a hardware component without which a computer
cannot be connected over a network. It is a circuit board installed in a computer that
provides a dedicated network connection to the computer. It is also called network
interface controller, network adapter or LAN adapter.
Purpose:
✓ NIC allows both wired and wireless communications.
✓ NIC allows communications between computers connected via local area
network (LAN) as well as communications over large-scale network through
Internet Protocol (IP).
✓ NIC is both a physical layer and a data link layer device, i.e. it provides the
necessary hardware circuitry so that the physical layer processes and some data
link layer processes can run on it.
https://www.tutorialspoint.com/what-is-network-interface-card-nic (reference)
5. What is MAC?
Ans: Mac Address is a unique identifier that is assigned to a NIC (Network
Interface Controller/ Card). It consists of a 48 bit or 64-bit address, which is
associated with the network adapter. MAC address can be in hexadecimal
format. The full form of MAC address is Media Access Control address.
➢ Address Type:
✓ Physical Address
A physical address is a memory address that is represented in the form of
a binary number on the address bus circuitry in order to enable the data
bus to access a particular storage cell of main memory.
✓ Logical Address
A logical address or virtual address is an address that is generated by the
CPU during program execution. The logical address is used as a
reference to access the physical address.
https://www.guru99.com/what-is-mac-address.html (reference)

6. What is Port?
Ans: A port is a virtual point where network connections start and end. Ports are software-
based and managed by a computer's operating system. Each port is associated with a specific
process or service. Ports allow computers to easily differentiate between different kinds of
traffic: emails go to a different port than webpages, for instance, even though both reach a
computer over the same Internet connection.
The different ports:
1. Ports 20 and 21: File Transfer Protocol (FTP).
2. Port 22: Secure Shell (SSH).
3. Port 25: Simple Mail Transfer Protocol (SMTP).
4. Port 53: Domain Name System (DNS).
5. Port 80: Hypertext Transfer Protocol (HTTP).
6. Port 123: Network Time Protocol (NTP).
7. Port 179: Border Gateway Protocol (BGP).
8. Port 443: HTTP Secure (HTTPS).
9. Port 23: Teletype Network (Telnet)
10. Port 110: Post office protocol 3(POP3).
11. Port 144: Internet message access protocol 4(IMAP4).
12. Port 67: Dynamic Host Configuration Protocol (DHCP/BOOTPS).
13. Port 69: Trivial File Transfer Protocol (TFTP).
14. Port 161: Simple Network Management Protocol (SNMP).
15. Port 520: performance improvement plan (PIP).
16. Port 143: Internet Message Access Protocol (IMAP)
17. Port 513: Internet Port.
18. Port 110: Electronic mail port.
https://www.cloudflare.com/learning/network-layer/what-is-a-computer-port (reference)

7. What is Hub?
Ans: A hub is basically a multiport repeater. A hub connects multiple wires coming
from different branches, for example, the connector in star topology which connects
different stations. Hubs cannot filter data, so data packets are sent to all connected
devices. In other words, collision domain of all hosts connected through Hub remains
one. Also, they do not have the intelligence to find out best path for data packets
which leads to inefficiencies and wastage.
8. What is Switch?
Ans: A switch is a device in a computer network that connects other devices together.
Multiple data cables are plugged into a switch to enable communication between
different networked devices.
9. What is Router?
Ans: A router is a device like a switch that routes data packets based on their IP
addresses. Router is mainly a Network Layer device.
10. What is Bridge?
Ans: A bridge operates at data link layer. A bridge is a repeater, with add on the
functionality of filtering content by reading the MAC addresses of source and
destination.
11. What Is Repeater?
Ans: A repeater operates at the physical layer. Its job is to regenerate the signal over
the same network before the signal becomes too weak or corrupted so as to extend the
length to which the signal can be transmitted over the same network.
12. What is Gateway?
Ans: A gateway, as the name suggests, is a passage to connect two networks
together that may work upon different networking models.
13. What is Brouter?
Ans: It is also known as bridging router is a device which combines features of both
bridge and router. It can work either at data link layer or at network layer.
https://www.geeksforgeeks.org/network-devices-hub-repeater-bridge-switch-router-gateways
(reference)

14. What is OSI Model?
Ans: The OSI Model is a conceptual framework used to describe the functions of a
networking system. The OSI model characterizes computing functions into a universal
set of rules and requirements in order to support interoperability between different
products and software.
7 Layers of the OSI Model:

1. Physical Layer: The lowest layer of the OSI reference model is the physical layer.
It is responsible for transmitting individual bits from one node to the next. When
receiving data, this layer will get the signal received and convert it into 0s and 1s and
send them to the Data Link layer.
2. Data Link Layer: The data link layer is responsible for the node to node delivery of
the message. When a packet arrives in a network, it is the responsibility of DLL to
transmit it to the Host using its MAC address.
3. Network Layer: Network layer works for the transmission of data from one host to
the other located in different networks. The sender & receiver’s IP address are placed
in the header by the network layer.
4. Transport Layer: Transport layer provides services to application layer and takes
services from network layer. The transport layer also provides the acknowledgement
of the successful data transmission and re-transmits the data if an error is found.
5. Session Layer: This layer allows a process to add checkpoints which are considered
as synchronization points into the data. These synchronization point help to identify the
error so that the data is re-synchronized properly, and ends of the messages are not cut
prematurely and data loss is avoided.
6. Presentation Layer: Presentation layer is also called the Translation layer.The
data from the application layer is extracted here and manipulated as per the required
format to transmit over the network.
7. Application Layer: At the very top of the OSI Reference Model stack of layers, we
find Application layer which is implemented by the network applications. These
applications produce the data, which has to be transferred over the network.
https://www.imperva.com/learn/application-security/osi-model (reference)

15. What Is the TCP/IP Model?
Ans: TCP/IP stands for Transmission Control Protocol/ Internet Protocol. TCP/IP
Model helps you to determine how a specific computer should be connected to the
internet and how data should be transmitted between them. It helps you to create a
virtual network when multiple computer networks are connected together. The purpose
of TCP/IP model is to allow communication over large distances.
Four Layers of TCP/IP Model:
➢ Application Layer
Application layer interacts with an application program, which is the highest level
of OSI model. The application layer is the OSI layer, which is closest to the end-
user. It means the OSI application layer allows users to interact with other
software application.
➢ Transport Layer
Transport Layer: The transport layer also offers an acknowledgment of the
successful data transmission and sends the next data in case no errors occurred.
TCP is the best-known example of the transport layer.
➢ Internet Layer
The Internet layer offers the functional and procedural method for transferring
variable length data sequences from one node to another with the help of various
networks. The main work of this layer is to send the packets from any network,
and any computer still they reach the destination irrespective of the route they
take.
➢ The Network Interface Layer
Network Interface Layer is this layer of the four-layer TCP/IP model. This layer is
also called a network access layer. It helps you to define details of how data
should be sent using the network.
https://www.guru99.com/tcp-ip-model.html (reference)

16. What is DATA REPRESENTATION?
Ans: Data is collection of raw facts which is processed to deduce information.
Data Communications Follows:
➢ Text
✓ Text includes combination of alphabets in small case as well as upper
case.
✓ It is stored as a pattern of bits. Prevalent encoding system, ASCII,
Unicode
➢ Numbers
✓ Numbers include combination of digits from 0 to 9.
✓ It is stored as a pattern of bits. Prevalent encoding system: ASCII, Unicode
➢ Images
✓ An image is worth a thousand words‖ is a very famous saying. In
computers images are digitally stored.
✓ A Pixel is the smallest element of an image. To put it in simple terms, a
picture or image is a matrix of pixel elements.
➢ Audio
✓ An image is worth a thousand words‖ is a very famous saying. In
computers images are digitally stored. A Pixel is the smallest element of
an image. To put it in simple terms, a picture or image is a matrix of pixel
elements.
✓ Video refers to broadcasting of data in form of picture or movie
➢ Video
✓ Video refers to broadcasting of data in form of picture or movie.
17. What is Data Flow?
Ans: Data Flow are devices communicate with each other by sending and receiving
data.
Data Flow between the two devices following this ways:

➢ Simplex
✓ In Simplex, communication is unidirectional
✓ Only one of the devices sends the data and the other one only
receives the data.
✓ Example: in the above diagram: a cpu send data while a monitor only
receives data
➢ Half Duplex
✓ In half duplex both the stations can transmit as well as receive but
not at the same time.
✓ When one device is sending other can only receive and viceversa (as
shown in figure above
✓ Example: A walkie-talkie.
➢ Full Duplex
✓ In Full duplex mode, both stations can transmit and receive at the
same time.
✓ Example: mobile phone.
https://techienutzz.wordpress.com/2016/09/25/data-flow-in-computer-network (reference)
18. What is IP Address?
Ans: An IP address is a unique address that identifies a device on the internet or a
local network. IP stands for "Internet Protocol," which is the set of rules governing the
format of data sent via the internet or local network.
Types of IP:
➢ IPV4-32 bit
➢ IPV6-128 bit

IPV4
8-Bit 8-Bit 8-Bit 8-Bit = 32 Bit
Class of IP:
IP Address IP Rang Possible Noof Host
Calss A 1-126 16,777,214
Class B 128-191 65,534
Class C 192-223 254
Class D 224-239
Class E 240-255
Class A:
Network Host Host Host
8 Bit 8 Bit 8 Bit 8 Bit
Class B:
Network Network Host Host
Class C:
Network Network Network Host

IP Address
➢ Private IP Address.
Private IP address of a system is the IP address which is used to communicate
within the same network. Using private IP data or information can be sent or
received within the same network.
The Private Address Blocks Area
✓ 10.0.0.0 To 10.255.255.255
✓ 172.16.0.0 To 172.31.255.255
✓ 192.168.0.0 To 192.168.255.255
➢ Public IP Address.
Public IP address of a system is the IP address which is used to communicate
outside the network. Public IP address is basically assigned by the ISP (Internet
Service Provider).
The Public IP Address Blocks Area
✓ Besides private IP addresses,
✓ Rest are public IP address.
https://www.geeksforgeeks.org/difference-between-private-and-public-ip-addresses (reference)

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